Solution-Doped Polysilicon Passivating Contacts for Silicon Solar Cells

Abstract

In this work, we present a simple and efficient solution-doping process for preparing high-quality polycrystalline silicon (poly-Si)-based passivating contacts. Commercial phosphorus or boron-doping solutions are spin-coated on crystalline silicon (c-Si) wafers that feature SiO2/poly-Si layers; the doping process is then activated by thermal annealing at high temperatures in a nitrogen atmosphere. With optimized n- and p-type solution doping and thermal annealing, n- and p-type poly-Si passivating contacts featuring simultaneously a low contact recombination parameter (J 0c) of 2.4 and 12 fA/cm2 and a low contact resistivity (ρc) of 29 and 20 mΩ·cm2 are achieved, respectively. Taking advantage of the single-sided nature of these solution-doping processes, c-Si solar cells with poly-Si passivating contacts of opposite polarity on the respective wafer surfaces are fabricated using a simple coannealing process, achieving the best power conversion efficiency (PCE) of 18.5% on a planar substrate. Overall, the solution-doping method is demonstrated to be a simple and promising alternative to gas/ion implantation doping for poly-Si passivating-contact manufacturing.

Computational Exploration Toward Tunnel Oxide Passivated Contact (TOPCon) Solar Cells: Tailoring Higher Efficiency

“…Therefore, proper matching of SiO x thickness and dopant concentration is critical to achieving excellent properties in terms of passivation and tunneling current in TOPCon solar cells. [ 27,28 ]…”

“…It has been proved that an oxide of 1.0 nm is sufficient to keep the V OC stable even when the rear‐SRV reaches 1 × 10 7 cm s –1 , and this might be because the oxide suppresses the leakage current. [ 27 ] The front‐SRV is also considered in our study, and the simulation results are shown in Figure 5b. The front‐SRV refers to the carrier recombination rate between a‐Si (p + ) and ITO.…”

“…Therefore, proper matching of SiO x thickness and dopant concentration is critical to achieving excellent properties in terms of passivation and tunneling current in TOPCon solar cells. [27,28] The role of the doped Si films that are deposited later (usually ≈10 nm) is to regulate the concentration of various kinds of carriers in the contact areas. The doped layer has the effect of socalled "field-effect" passivation, which repels one kind of carrier and is also an efficient way to reduce recombination.…”

Investigation of Gallium–Boron Spin‐On Codoping for poly‐Si/SiOx Passivating Contacts

“…[ 25 ] Among them, spin‐on doping is currently attracting interest from the photovoltaic research community due to its convenience and simplicity. [ 26,27 ] The source of dopants for the spin‐on process is a solution of dopant‐containing silicate glass in alcohol. This glass solution can be easily spun onto the Si wafer at room temperature.…”

“…This glass solution can be easily spun onto the Si wafer at room temperature. For higher throughput, such as in an industrial manufacturing line, the solution can potentially be sprayed, [ 25 ] tape cast, [ 28 ] spin‐coated, [ 27 ] or inkjet‐printed. [ 29 ] In addition, this spin‐on doping method brings the benefit of using less toxic precursors compared with conventional gas diffusion or ion implantation processes.…”